Scala Library
scala

trait Seq
[source: scala/Seq.scala]
trait Seq[+A]
extends PartialFunction[Int, A] with Collection[A]
Class Seq[A] represents finite sequences of elements of type A.
Author
Martin Odersky
Matthias Zenger
Version
1.0, 16/07/2003
Direct Known Subclasses:
List, RandomAccessSeq, Seq.Projection, SeqProxy, Queue, Stack, MutableSeq, Buffer, MutableList, SingleLinkedList, Stack, NodeSeq
Method Summary
override def ++ [B >: A](that : Iterable[B]) : Seq[B]
Appends two iterable objects.
override def concat [B >: A](that : Iterable[B]) : Seq[B]
Appends two iterable objects.
def contains (elem : Any) : Boolean
Tests if the given value elem is a member of this sequence.
def containsSlice [B](that : Seq[B]) : Boolean
Is that a slice in this?
override def drop (n : Int) : Seq[A]
Returns this sequence without its n first elements If this sequence has less than n elements, the empty sequence is returned. (non-strict)
override def dropWhile (p : (A) => Boolean) : Seq[A]
Returns the longest suffix of this sequence whose first element does not satisfy the predicate p.
def endsWith [B](that : Seq[B]) : Boolean
def equalsWith [B](that : Seq[B])(f : (A, B) => Boolean) : Boolean
override def filter (p : (A) => Boolean) : Seq[A]
Returns all the elements of this sequence that satisfy the predicate p. The order of the elements is preserved.
override def findIndexOf (p : (A) => Boolean) : Int
Returns index of the first element satisying a predicate, or -1.
def first : A
Returns the first element of this list.
def firstOption : Option[A]
Returns as an option the first element of this list or None if list is empty.
override def flatMap [B](f : (A) => Iterable[B]) : Seq[B]
Applies the given function f to each element of this sequence, then concatenates the results.
def headOption : Option[A]
def indexOf [B >: A](that : Seq[B]) : Int
Searches for the argument sequence in the receiver object, returning the smallest index where a match occurs. If the receiver object, this, is an infinite sequence this method will not terminate if there is no match. Similarly, if the both the receiver object and the argument, that are infinite sequences this method will not terminate. Because both the receiver object and the argument can both potentially be an infinite sequences, we do not attempt to use an optimized searching algorithm. Therefore, the running time will be proportional to the length of the receiver object and the argument. Subclasses and traits can potentially provide an optimized implementation.
override def indexOf [B >: A](elem : B) : Int
Returns the index of the first occurence of the specified object in this iterable object.
def isDefinedAt (x : Int) : Boolean
Is this partial function defined for the index x?
override def isEmpty : Boolean
Returns true if length == 0
def last : A
Returns the last element of this list.
def lastIndexOf [B >: A](elem : B) : Int
Returns the index of the last occurence of the specified element in this sequence, or -1 if the sequence does not contain this element.
def lastOption : Option[A]
Returns as an option the last element of this list or None if list is empty.
abstract def length : Int
Returns the length of the sequence.
def lengthCompare (l : Int) : Int
Result of comparing length with operand l. returns x where x < 0 iff this.length < l x == 0 iff this.length == l x > 0 iff this.length > that. This method is used by matching streams against right-ignoring (...,_*) patterns. Lazy sequences should override this method if length forces evaluation of the stream.
override def map [B](f : (A) => B) : Seq[B]
Returns the sequence resulting from applying the given function f to each element of this sequence.
override def projection : Projection[A]
returns a projection that can be used to call non-strict filter, map, and flatMap methods that build projections of the collection.
def reverse : Seq[A]
A sequence consisting of all elements of this sequence in reverse order.
def size : Int
should always be length
def slice (from : Int) : Seq[A]
A sub-sequence starting at index from and extending up to the length of the current sequence (non-strict)
def slice (from : Int, until : Int) : Seq[A]
A sub-sequence starting at index from and ending (non-inclusive) at index until (non-strict)
def startsWith [B](that : Seq[B]) : Boolean
Check whether the receiver object starts with the argument sequence.
def startsWith [B](that : Seq[B], offset : Int) : Boolean
Checks whether the argument sequence is contained at the specified index within the receiver object. If the both the receiver object, this and the argument, that are infinite sequences this method may not terminate.
def subseq (from : Int, end : Int) : Seq[A]
Returns a subsequence starting from index from consisting of len elements.
override def take (n : Int) : Seq[A]
Returns a sequence consisting only over the first n elements of this sequence, or else the whole sequence, if it has less than n elements. (non-strict)
override def takeWhile (p : (A) => Boolean) : Seq[A]
Returns the longest prefix of this sequence whose elements satisfy the predicate p.
override def toArray [B >: A] : Array[B]
Converts this sequence to a fresh Array with length elements.
override def toSeq : Seq[A]
Overridden for efficiency.
Methods inherited from Collection
toString, stringPrefix
Methods inherited from Iterable
elements (abstract), partition, foreach, forall, exists, find, foldLeft, foldRight, /:, :\, reduceLeft, reduceRight, copyToBuffer, sameElements, toList, toStream, mkString, mkString, mkString, addString, addString, addString, copyToArray, hasDefiniteSize
Methods inherited from PartialFunction
orElse, andThen
Methods inherited from Function1
apply (abstract), compose
Methods inherited from AnyRef
getClass, hashCode, equals, clone, notify, notifyAll, wait, wait, wait, finalize, ==, !=, eq, ne, synchronized
Methods inherited from Any
==, !=, isInstanceOf, asInstanceOf
Method Details
abstract def length : Int
Returns the length of the sequence.
Returns
the sequence length.
def lengthCompare(l : Int) : Int
Result of comparing length with operand l. returns x where x < 0 iff this.length < l x == 0 iff this.length == l x > 0 iff this.length > that. This method is used by matching streams against right-ignoring (...,_*) patterns. Lazy sequences should override this method if length forces evaluation of the stream.
def size : Int
should always be length
Overrides
Collection.size
override def isEmpty : Boolean
Returns true if length == 0
@deprecated

override def concat[B >: A](that : Iterable[B]) : Seq[B]
Appends two iterable objects.
Returns
the new iterable object
Deprecated
use ++ instead
def last : A
Returns the last element of this list.
Returns
the last element of the list.
Throws
Predef.NoSuchElementException - if the list is empty.
def lastOption : Option[A]
Returns as an option the last element of this list or None if list is empty.
Returns
the last element as an option.
def first : A
Returns the first element of this list.
Returns
the first element of the list.
Throws
Predef.UnsupportedOperationException - if the list is empty.
def firstOption : Option[A]
Returns as an option the first element of this list or None if list is empty.
Returns
the first element as an option.
@deprecated

def headOption : Option[A]
override def ++[B >: A](that : Iterable[B]) : Seq[B]
Appends two iterable objects.
def isDefinedAt(x : Int) : Boolean
Is this partial function defined for the index x?
Parameters
x - ..
Returns
true, iff x is a legal sequence index.
Overrides
PartialFunction.isDefinedAt
def lastIndexOf[B >: A](elem : B) : Int
Returns the index of the last occurence of the specified element in this sequence, or -1 if the sequence does not contain this element.
Parameters
elem - element to search for.
Returns
the index in this sequence of the last occurence of the specified element, or -1 if the sequence does not contain this element.
override def findIndexOf(p : (A) => Boolean) : Int
Returns index of the first element satisying a predicate, or -1.
Notes
may not terminate for infinite-sized collections.
Parameters
p - the predicate
Returns
the index of the first element satisfying p, or -1 if such an element does not exist
override def indexOf[B >: A](elem : B) : Int
Returns the index of the first occurence of the specified object in this iterable object.
Notes
may not terminate for infinite-sized collections.
Parameters
elem - element to search for.
Returns
the index in this sequence of the first occurence of the specified element, or -1 if the sequence does not contain this element.
override def map[B](f : (A) => B) : Seq[B]
Returns the sequence resulting from applying the given function f to each element of this sequence.
Parameters
f - function to apply to each element.
Returns
f(a0), ..., f(an) if this sequence is a0, ..., an.
override def flatMap[B](f : (A) => Iterable[B]) : Seq[B]
Applies the given function f to each element of this sequence, then concatenates the results.
Parameters
f - the function to apply on each element.
Returns
f(a0) ::: ... ::: f(an) if this sequence is a0, ..., an.
override def filter(p : (A) => Boolean) : Seq[A]
Returns all the elements of this sequence that satisfy the predicate p. The order of the elements is preserved.
Parameters
p - the predicate used to filter the list.
Returns
the elements of this list satisfying p.
override def take(n : Int) : Seq[A]
Returns a sequence consisting only over the first n elements of this sequence, or else the whole sequence, if it has less than n elements. (non-strict)
Parameters
n - the number of elements to take
Returns
a possibly projected sequence
override def drop(n : Int) : Seq[A]
Returns this sequence without its n first elements If this sequence has less than n elements, the empty sequence is returned. (non-strict)
Parameters
n - the number of elements to drop
Returns
the new sequence
def slice(from : Int, until : Int) : Seq[A]
A sub-sequence starting at index from and ending (non-inclusive) at index until (non-strict)
Parameters
from - The index of the first element of the slice
until - The index of the element following the slice
Throws
IndexOutOfBoundsException - if from < 0 or length < from + len
@deprecated

def slice(from : Int) : Seq[A]
A sub-sequence starting at index from and extending up to the length of the current sequence (non-strict)
Parameters
from - The index of the first element of the slice
Throws
IndexOutOfBoundsException - if from < 0
Deprecated
Use drop(n: Int): Seq[A] instead.
override def takeWhile(p : (A) => Boolean) : Seq[A]
Returns the longest prefix of this sequence whose elements satisfy the predicate p.
Parameters
p - the test predicate.
Returns
the longest prefix of this sequence whose elements satisfy the predicate p.
override def dropWhile(p : (A) => Boolean) : Seq[A]
Returns the longest suffix of this sequence whose first element does not satisfy the predicate p.
Parameters
p - the test predicate.
Returns
the longest suffix of the sequence whose first element does not satisfy the predicate p.
def reverse : Seq[A]
A sequence consisting of all elements of this sequence in reverse order.
def contains(elem : Any) : Boolean
Tests if the given value elem is a member of this sequence.
Parameters
elem - element whose membership has to be tested.
Returns
true iff there is an element of this sequence which is equal (w.r.t. ==) to elem.
@deprecated

def subseq(from : Int, end : Int) : Seq[A]
Returns a subsequence starting from index from consisting of len elements.
Deprecated
use slice instead
override def toArray[B >: A] : Array[B]
Converts this sequence to a fresh Array with length elements.
Overrides
Collection.toArray
override def toSeq : Seq[A]
Overridden for efficiency.
Returns
the sequence itself
override def projection : Projection[A]
returns a projection that can be used to call non-strict filter, map, and flatMap methods that build projections of the collection.
def equalsWith[B](that : Seq[B])(f : (A, B) => Boolean) : Boolean
def startsWith[B](that : Seq[B], offset : Int) : Boolean
Checks whether the argument sequence is contained at the specified index within the receiver object. If the both the receiver object, this and the argument, that are infinite sequences this method may not terminate.
Returns
true if that is contained in this, at the specified index, otherwise false
See Also
String.startsWith
def startsWith[B](that : Seq[B]) : Boolean
Check whether the receiver object starts with the argument sequence.
Returns
true if that is a prefix of this, otherwise false
See Also
Seq.startsWith
def endsWith[B](that : Seq[B]) : Boolean
Returns
true if this sequence end with that sequence
See Also
String.endsWith
def indexOf[B >: A](that : Seq[B]) : Int
Searches for the argument sequence in the receiver object, returning the smallest index where a match occurs. If the receiver object, this, is an infinite sequence this method will not terminate if there is no match. Similarly, if the both the receiver object and the argument, that are infinite sequences this method will not terminate. Because both the receiver object and the argument can both potentially be an infinite sequences, we do not attempt to use an optimized searching algorithm. Therefore, the running time will be proportional to the length of the receiver object and the argument. Subclasses and traits can potentially provide an optimized implementation.
Returns
-1 if that not contained in this, otherwise the smallest index where that is found.
See Also
String.indexOf
def containsSlice[B](that : Seq[B]) : Boolean
Is that a slice in this?
Scala Library